1. Field of the Invention
This invention relates to the field of torque converters for automatic transmissions. More particularly the instant invention pertains to the hub of a bladed wheel, such as an impeller, stator or turbine wheel.
2. Description of the Related Art
Automatic transmissions of the type employed in motor vehicles, commonly employ a mechanical gear train and a hydrokinetic torque converter on the input side of the transmission. The torque converter includes several rotating wheels fitted with radially extending vanes or blades, one of which is the driving member or impeller, another is the driven member or turbine. When assembled, the impeller and turbine define a toroidal cavity or chamber wherein hydraulic oil exiting the engine-driven impeller drives the turbine and the mechanical gear train driveably connected to the turbine.
Conventionally the components of the torque converters are formed from 1010 structural steel having a hardness of Rb 80. After extended service, the hub may become scored, or worn to a reduced size, or both. This wear directly, adversely affects the integrity of a seal that contacts the hub, and requires that the hub be either reconditioned or replaced. It has previously been necessary either to replace the entire impeller or turbine assembly with a new one, or to remove the tubular hub portion of the assembly and replace it with a new assembly.
Other than the expensive replacement of one or more components, various repair methods are known. One repair method generally practiced includes removing the integral hub by heating a weld between the housing and hub, and welding a new hub to the housing. In another method, the welded joint between the hub and the impeller cover or turbine housing is simply cut away and a new hub is welded to the assembly. As a practical matter, the concentricity of the outer surface of the hub must be corrected after a new hub is installed.
A further method used to recondition a worn torque converter hub is disclosed by Scholz in U.S. Pat. No. 4,212,187. Scholz teaches the use of an expansion tool to expand diametrically a worn impeller hub. The hub is expanded to a diameter greater than its original condition, then ground and finished to the original diameter.
Unfortunately, Scholz's expansion and grinding of the original hub decreases the final material thickness and weakens the hub. Further, as the hub still consists of the original material, the hub will wear in the same manner, and the problem will recur.
It is therefor desirable to provide a method for refurbishing a worn torque converter hub that is both inexpensive to execute and produces a durable product.